A major obstacle in the precision connection of optical fibers, MTP connectors and similar devices is the critical alignment of an optical waveguide to its signal input and output and pump sources. This is especially important when various optical components are interfaced to a multi-fiber ribbon when used in conjunction with a single or multichannel waveguide. Current alignment techniques include active alignment and passive alignment.
Active alignment involves pigtailing fibers individually by automated machine vision with motorized stages. For example, a waveguide substrate potentially has a number of channels that are aligned with fibers by actively passing light through the fibers and/or devices to align the fibers. A power meter is typically used to measure the percentage of light passing through the connected device and fiber to assure that the fiber alignment is correct. Once any fiber and connector alignment is determined to be correct, epoxy is applied over the waveguide substrate and fiber to bond and cure the fibers into a set position. This active alignment process is a very labor intensive process, requiring high skill and the use of high precision opto-mechanical alignment systems.
Passive alignment overcomes the drawbacks associated with the active alignment, and is used for connecting MTP multi-fiber connectors and similarly designed optical connector applications. The MTP connector assembly includes a precise multi-fiber array and ferrule and a passive alignment mechanism formed by two guide holes and pins. An example of such a passive alignment MTP connector assembly is disclosed in the technical paper, “MT Multifiber Connectors and New Applications”, 44th Electronic Components and Technology Conference, 1994, the disclosure of which is hereby incorporated by reference in its entirety.
A passive alignment accuracy of 2 micrometers has been obtained using this technique. The passive alignment between a multimode 12-fiber ribbon terminated with the MT (or MTP) connector and a vertical cavity surface emitting laser (VCSEL) array giving a 10 micrometer active diameter held a high percentage of coupling efficiency. This allowed a multi-fiber ribbon to a multi-fiber ribbon connection using an intermediate connector as described.
Another problem arises when multi-fiber ribbons are used in applications requiring amplification of the optical signals being transported by the fibers, such as in long haul non-regenerative repeaters. To amplify the optical signals, it is necessary to break out each individual fiber from the multi-fiber ribbon. This is a very labor intensive process.
One approach for avoiding this process is disclosed in U.S. Pat. No. 6,594,420 to Lange et al., which is assigned to the current assignee of the present invention and is incorporated herein by reference in its entirety. In Lange et al., optical waveguides are optically coupled to an array of optical pump sources through an optical coupler. However, Lange et al. fails to disclose in any detail how the optical coupler is aligned with the optical waveguides. Instead, Lange et al. simply discloses that the optical coupler is arranged immediately adjacent an upper surface of the optical waveguides.